Cross-reference is hereby made to commonly assigned and copending U.S. application Ser. No. 09/219,725, entitled Xeromorph Electrostatic Cleaning Brush, filed Dec. 22, 1998 by Christopher Snelling and Dale Mashtare, and U.S. application Ser. No. 09/218,672, entitled Cleaning Brush Using the Pyroelectric Effect, filed Dec. 22, 1998 by Dale Mashtare and Christopher Snelling.
This invention relates to a printing apparatus and more particularly to a cleaning apparatus for removing residual particles, such as, toner from a charge retentive surface forming a part of the printing apparatus with subsequent removal of the toner particles from the cleaning apparatus.
In printing arts of the type contemplated, one method of forming images is using a charge retentive surface such as a photoreceptor or photoconductor. It comprises a photoconductive insulating material adhered to a conductive backing which is charged uniformly. Then the photoreceptor is exposed to a light image of an original document to be reproduced. The latent electrostatic images, thus formed, are rendered visible by applying any one of numerous pigmented resins specifically designed for this purpose. In this case of a reusable photoreceptor, the pigmented resin, more commonly referred to as toner which forms the visible images is transferred to plain paper. After transfer, the toner images are made to adhere to the copy medium usually through the application of heat and pressure by means of a roll fuser.
Although a preponderance of the toner forming the images is transferred to the paper during transfer, some toner remains on the photoreceptor surface, it being held thereto by relatively high electrostatic and/or mechanical forces. It is essential for optimum operation that the toner and debris remaining on the surface be cleaned thoroughly therefrom.
A commercially successful mode of cleaning employed in automatic xerography utilizes a brush with soft bristles which have suitable triboelectric characteristics. While the bristles are soft they are sufficiently soft to remove residual toner particles from the xerographic plate. In addition, webs or belts of soft fibrous or tacky materials and other cleaning systems are known.
More recent developments in the area of removing residual toner and debris from a charge retentive surface have resulted in cleaning structures which, in addition to relying on the physical contacting of the surface to be acted upon also rely on electrostatic fields established by electrically biasing one or more members of the cleaner system.
It has been found that establishing an electrostatic field between the charge retentive surface and the cleaning member such as a fiber brush or a magnetic brush enhances toner attraction to the cleaning brush surface. Such arrangements are disclosed in U.S. Pat. Nos. 3,572,923, and 3,722,018 granted to Fisher et al. on Mar. 22, 1973 and Fisher on Mar. 30, 1971, respectively. Likewise, when an electrostatic field is established between the brush and a brush detoning member, removal of toner from the brush is improved, as shown in, for example, U.S. Pat. No. 4,705,387. The creation of the electrostatic field between the brush and photoreceptor is accomplished by applying a D.C. voltage to the brush. When the fibers of granules forming the brush are electrically conductive and a bias is applied thereto cleaning is observed to be more efficient than if the fibers are non-conductive or insulative.
In accordance with the improved features of the present invention, there is provided an active electrostatic cleaning brush for removing toner particles from a surface with subsequent separation of particles having a predetermined diameter and charge from the cleaning brush. In one embodiment, the active electrostatic cleaning brush is made of flexible piezoelectric fibers. The brush fibers are made in one embodiment from a bi-layer plastic; one of which is poled polyvinylidenefluoride (PVDF) covered over a conductive core. Upon bending, the fiber will generate an electrostatic potential on its surface that will attract and hold oppositely charged toner, which will then be released when the fiber is flexed in an opposite direction.
In another embodiment, the active electrostatic cleaning brush includes a hub and flexible fibers extending from the hub. The flexible fibers comprise a bi-layer of polyvinylidene fluoride film supported by a grounded conductive member.